The present invention relates to a light transmitting type screen,in which images projected from its back side by a projector are seen from the side opposite the projector. Particularly, it relates to a light transmitting type screen excellent in transparency and making it possible to see through to the background behind the screen by employing a light scattering layer with a special light scattering property.
Conventionally, most practical light transmitting type screens use polarization films, Fresnel lens sheets, lenticular lens sheets, etc. in order to obtain high brightness and high contrast. However, such conventional light transmitting type screens are expensive because polarization films and lens sheets are high in cost, and it is almost impossible to see the background behind the screens.
A common way of advertising merchandize is to stick posters on show windows or to apply spray paint to show windows. These advertising displays are static and the contents thereof do not change unless the posters or spray paint displays are replaced. Use of a projector or the like might be considered for displaying dynamic advertisements on show windows, but projected images cannot be formed on show windows because of their high transparency.
Although an image projected from the back side can be seen if a conventional light transmitting type screen is attached to a show window, the presence of the screen makes it impossible to see displayed goods from the outside. The show window is therefore deprived of its function by the inability to see through the light transmitting type screen.
Accordingly, an object of the present invention is to provide a light transmitting type screen that enables the viewer to see through to its back side when the screen is adhered to a transparent object such as a show window or a transparent window glass or when it is used as a transparent object for forming clear images projected from a projector thereon.
The present inventors have found that projected images are clearly formed on a screen made from materials having a front-scattering property while objects behind the screen can be seen from the front. Front-scattering is an optical property whereby most incident light is scattered forward and little or no light backward. Front-scattering is caused by Mie scattering, that is, light scattering caused by spherical dielectric particles having a far larger diameter than the wavelength of light.
Specifically, the see-through light transmitting type screen of the present invention is characterized in that it has a light scattering layer having a front-scattering property.
The light scattering layer comprises a transparent binder and spherical microparticles. The spherical microparticles preferably have a mean particle diameter of 1.0 xcexcm-10.0 xcexcm and a refraction index (n) relative to the refraction index of the transparent binder satisfying a condition of 0.91 less than n less than 1.09 (nxe2x89xa0100 ). The transparent binder may be glass or high molecular weight resin.
The see-through light transmitting type screen of the present invention may include a transparent object provided on at least one side of the light scattering layer, disposed on the projector side or on the viewer side. The transparent object, if disposed on the projector side, preferably has a refraction index lower than that of the transparent binder of the light scattering layer. If disposed on the viewer side the transparent object has a refraction index higher than that of the transparent binder of the light scattering layer.
Optionally, an anti-reflection layer is provided on at least one side of the screen.
The see-through light transmitting type screen of the present invention preferably has a haze of 3.0% or more and distinctness of image of 60.0% or more.
The term xe2x80x9chazexe2x80x9d used with respect to the present invention means a haze value determined in accordance with JIS-K7 105, which can be calculated according to the equation:
H=[Td/Tt]xc3x97100[H: haze, Td: diffused light transmission, and Tt: total light transmission].
The term xe2x80x9cdistinctness of imagexe2x80x9d used with respect to the present invention means a value of distinctness of image determined in accordance with JIS-K7105, and it can be obtained by measuring the maximum wave height [M] and the minimum wave height [m] at an optical comb of 0.125 mm using the transmission method, and calculating according to the following equation:
Distinctness of image [C(0.125)={Mxe2x88x92m}/{M+m}xc3x97100(%)
The value of distinctness of image used for the present invention is an average of values measured along the longitudinal direction and the transverse direction for each sample.